Storage Subsystem and Method of Executing Commands by Controller

1. A storage subsystem comprising: a plurality of hard disk drives; and a controller configured to execute a plurality of commands received from a host computer coupled to the controller for the plurality of hard disk drives and to determine whether each received command is a priority command based on priority command information that defines attributes of command, and wherein, for each received command, upon determining that the received command is not a priority command, the controller adds the received command to a non-priority command queue, wherein, for each received command, upon determining that the received command is a priority command, unless a quantity of priority commands to be executed during a predetermined time period is greater than a predetermined value, the controller executes the received command in preference to each received command to be executed during the predetermined time period in the non-priority command queue, and wherein the controller successively executes each received command to be executed during the predetermined time period that is determined to be a priority command in preference to each received command to be executed during the predetermined time period in the non-priority command queue within said predetermined time period until said predetermined value of priority commands have been executed.

2. A storage subsystem as set forth in claim 1 , wherein each priority command is one of an inquiry command and a read capacity command, and each non-priority command is an I/O command.

3. A storage subsystem as set forth in claim 1 , wherein the priority command information includes a logical block address indicating a specified storage region in said hard disk drives.

4. A storage subsystem as set forth in claim 3 , wherein, if a received command is a command that designates the specified storage region, the controller determines said received command to be a priority command.

5. A storage subsystem as set forth in claim 1 , wherein said host computer includes a plurality of virtual machines, and wherein the virtual machines send said plurality of commands to said controller.

6. A storage subsystem as set forth in claim 1 , wherein the controller creates the priority command information based on a priority command-setting request sent from a management apparatus.

7. A method of executing commands for a plurality of hard disk drives from a host computer by a controller coupled to the host computer, said method comprising: receiving a plurality of commands from said host computer via a port; determining whether each received command is a priority command based on priority command information that defines attributes of commands; adding each received command that is determined to not be a priority command to a non-priority command queue; and for each received command that is determined to be a priority command, unless a quantity of priority commands to be executed during a predetermined time period is greater than a predetermined value, executing the received command in preference to each received command to be executed during the predetermined time period in the non-priority command queue, and wherein the received commands to be executed during the predetermined time period that are determined to be priority commands are successively executed in preference to each received command to be executed during the predetermined time period in the non-priority command queue within said predetermined time period until said predetermined value of priority commands have been executed.

8. A method of executing commands as set forth in claim 7 , wherein each priority command is one of an inquiry command and a read capacity command, and each non-priority command is an I/O command.

9. A method of executing commands as set forth in claim 7 , wherein the priority command information includes a logical block address indicating a specified storage region in said hard disk drives.

10. A method of executing commands as set forth in claim 9 , wherein, if a received command is a command that designates the specified storage region, said controller determines said received command to be a priority command.

11. A method of executing commands as set forth in claim 7 , further comprising creating the priority command information based on a priority command-setting request sent from a management apparatus.

12. A method of executing commands as set forth in claim 7 , wherein said controller receives the plurality of commands from a plurality of virtual machines included in the host computer via said port.